This invention relates to vector quantization with a universal codebook.
Vector quantization compresses a signal vector by representing the vector with a codevector chosen from a codebook. An index identifying the codevector is transmitted as the compressed output.
The codebook is typically designed for a signal vector having a particular probability distribution. For instance, the codevectors in the codebook may correspond to the most frequent values assumed by the signal vector, in order to minimize the distortion caused by compression.
When it becomes necessary to compress signals arising from different sources (and thus having significantly different probability distributions), a different codebook is required for each source in order to minimize distortion. The increased number of codebooks increases the storage requirements of the vector quantization scheme. To alleviate this problem, some vector quantization schemes require groups of sources to share codebooks.